Electrical jack



Jan. 9, 1945. H, M MoY I 'ELECTRICAL JACK Filed Jult 30, 1945 Patented Jan. 9, 1945 l g 2.366339V e Mmmm, p e, ,n y Howard McCoy, Fairfield, Qhm `kllllici'ltidn J ly 36, 1943, senaiNo. 496,651@ solenne k101.1925142) j f *The invention described herein may be manu-.jl

factured and usedby or for the Government for governmentalpurposes,y without the payment to,

me of any royalty thereon.' y

This invention relates to electrical governor controlsfor hydraulicallyoperated variable pitch, airplane propellers. Among other objects, the invention aims tov provide a vpositively acting mechanism of the character indicated'which may be used with automatically governed propellers, p'articularly'oi the hydraulic type. More specically, the invention provides a mechanismwhich permits a fine'adjustment oi' the governorspring lever by 'electricalmeans, thus making *possible remote controlY and synchronized action onseveral propellers simultaneously, also automatic and ,armatureV Bwith a yifnotorshait l'whichis n ly .to the motor housing by' studs s. Thusy they and adjustablecontrol oi.' -thelimits of' motion.v

In its broader aspects, the invention providesgan improvement in electrical jacks which converts the high speed rotary motion of a motor shaft into slow speed reciprocationfofl a rod whichl may actuate various devices, with sharply defined lim-r its of motion of the rod in either direction.r There are many uses for ksucha compact remotely controlled push-pull.' servo mechanism"particular-y lyinaircraft in the retraction of landing gears,v

englne'fcowl and Wing aps', control` surface `trirn tabs etc.

It has ,been 'proposed in the Houston Patent No. 1,942,100,dated'January 2, 19,34, Ato adjust the pitch of propellers during operation by means oi a linkage operated by a screw-threaded sleeve j` reciprocated by a nut driven by V'a worm gearing which derives its power from reversible motor under the control of the pilot. According to the`r Martin Patent No.V 2,144,429,rk dated January 17, 1939, a reversible motor drives 'a limit switch mechanism'of the'` traveling nut type which adf justs a governor to control` the speed'cfranairplane engine by lcontrolling the pitchof thepropeller, the propeller pitch beingjgoverned by varying the opening ofthe valvewhich 'controls the supply of hydraulic fluid to the propeller. ``In the Lear et al. patent, No. 2,267,114, dat'edjDecemr ber 23,'` 1941, ya servomotor visv shown `with a 'mag-` neticclutch which is energizedv lalong with the` servomotor that drives [the f clutch .and whichv brakes theload ywhen the servomotor is -de-ener` glzed. Myinvention employs one or more ci the features" of each ofthese patents, but provides hollowy end 'toA end'A and LisV supported by antifriction bearings "l5` .In the motor housing 6. The motorshaft projects `from' oneI end ofthe housing into av L,casing 1. which is preferablysecured directmotorhousing andcasing form inv effect a single housingwhich in `the preferred formucompletely encloses all ofthemechanisms lthat make up the unit except the power-delivering or push-pull member to be described. n n f "Fixed on the inside of rcasing .7v is a solenoid 9 whichv is inseries with the field winding 2, as will be understood withoutillustration, and which, therefore, isfenergized only when the motor is energized. y Adjacent to the solenoid, and in the magnetic ,neldthereoL is a clutch rplate I0 of magnetizablefinetal,fsuch as` softv iron, secured as by set screws `I I to the outer endo! the motorshai't so esto revolv'eltherewith. Hence plate I0 may be'ter'med the driving clutchplate. Another clutch,` plate I2 of' soft ironis iixed as by setv screws `I3 to aslidable sleeve I4 which also carries a coilspringy I5 under fcompressionbetween a gear I 6 secured tothe sleeve, and a ystationary brake disk I] secured to the casing with b'rakesegments I8 fixed upon the stationary brake diskII.` "However, the'magnetic attraction ofuihe driving clutch" plate I IJ4 for the driven plate I2 isof such power asg'to overcome the resistance of the spring andbring the two clutch plates into contact, whereupon vmagnetism will Ahold them rtogether without'slippagefso long as the solenoid is energized;y Indeed', the heavier the load on ythe motor,nconsequently on the clutch, the stronger the magnetic field which unites the ,l

` clutch'plates, ,'But when, the motor circuitA is a uniquejmechanism having certain advantages far as 'Iknowfv ness.r

Referring particularly to the drawing, a reversible motor I is shown having a field winding 2 which, arenot i found'i'n n' any prior artdevices,` `so broken, clutch plate I2 v'will be movedaway by spring I5 'andwill engagevthe brake'segments IB to stopthe sleeve I4 and the parts driven thereby. l As the -rapidly .rotating armature 'is then unclutched from thesleeve/the'latter is stopped quickly, while the armature is freefto spin until stopped by friction etc.

kGear lisp'referably part of'a planetary re-` ductiongearls'ystem and may bejtermed the sun gear otzthat system. 'apluralitylof' idler kor planet .gears I9, preferably three, mesh with the sun geanIB and also mesh with a" ring gear 20. The idler gears I9y are each rotatable on spindles .y Iii'y securedupon thenxed brake disk" I'I` and henceunever move aroundftheaxistof the ks un gear. Preferably/integral with the ring gear is a nut 2|, rotatably mounted on amanti-.friction bearing `2'2- securedina boss 23 integral with cas- 2 assenso ing 1. A plate 24 may be secured by studs 2l to the outer end of the boss to enclose the nut completely and to give access to the bearing. The ring gear and nut assembly is restrained against any motion except rotation. Slidable in the motorshaft 4 is a lead screw or jack screw 2i having single or multiple threads with which the nut 2l engages so as to reciprocate the lead screw aS the nut is driven in opposite directions by the reversible motor. One or both ends of the lead screw project beyond the motor housing i and casing 1, and either or both ends may have an unthreaded portion 20a with an eye 28h which exemplies a power take-oi! and facilitates securing a lever or any other member that is to be actuated by the lead screw. The tangential frictional component tending to turn the lead screw is normally resisted by whatever element is at-` tached to the eye lib. However, a longitudinal slot 21 may be cut in the lead screw to receive a key 28 fixed to the plate 2l, thus preventing any rotation of the lead screw or any rotative tendency which might bind or injure the limit switch mechanism. y

To limit movement of the lead screw in either direction, another longitudinal slot 2! is cut in the smooth portion 26a of the lead screw and a pair of switches 30 have insulating arms 3l which enter the slot 29 and are moved by contact with a shoulder 32 at either end of the slot to break the motor circuit, which is completed through fixed contact members 33. Switches 30 and contaci. members 33 are preferably enclosed in a switch box 34 mounted on casing 1. Adjustment of the limit of movement in either direction may be effected by employing screws I placed in any one of a series of tapped bores Il leading from the bottom of the slot 2l. The closer together the screws 35 are placed, the shorter the strokes ofthe reciprocating lead screw, since the insulating arms Il will break themotor circuit that much sooner.

The present invention provides a very powerful. compact unit which may have many uses on an airplane or wherever space is limited and a pushpull power take-olf is advantageous. The magnetic clutch permits the armature to instantaneously start without appreciable load until magnetic force is suiilcient to compress the spring Ii coupling the lead screw to the motor. When power is cut olf, the lead screw stops almost instantly, or in other words, the action is deadbeat. which is likewise advantageous since it permits a very nice control of any part operated by the lead screw. This braking action also prevents creeping of the lead screw under vibration. Other types of'reduction gearing may be empios-'ed in lieu oi. the planetary gears disclosed ,herein v.

Obviously, the invention may be embodied in several forms neither described nor shown.

WhatIclaimis: i

l. In combination'. 'a reversible motor; reduction gearing; a clutch automatically engaging and disengaging the motor from the reduction gearing when the motor is energized and deenergized, respectively; braking means for the gearing, said braking means acting when the clutch disengages the motor from the gearing; a nut driven by the gearing; a lead screw reciprocated -by the nut; means for preventing rotation of the lead screw; and power take-off means on the lead screw.

2. In combination, a reversible electric motor and a circuit therefor; a solenoid electrically connected in the motor circuit to be energired when the motor is energized and to be de-energiaod when the motor circuit is open; a clutch plate directly driven by the motorshaft, said clutch plate being in the magnetic field of the solenoid: a second magnetizable clutch plate nxed to a sleeve, said sleeve being slldable toward and from the nrst clutch plate; a spring holding the two clutch plates apart except when said plates are engaged by magnetic action; reduction gearing driven by said sleeve; a nxed braking disk which the magnetizable clutch plate frictionally engins by action of said spring when the solenoid is deenergised; a lead screw supported so as to move longitudinally of the axis of the motorshaft: means to prevent rotation of the lead screw; and a nut rotated by the reduction gearing and engazing the threads ot the lead screw, so that rotation of the nut moves the lead screw longitudinally.

3. The invention according to claim 2. wherein there is a casing which houses the solenoid. the clutch, the braking disk, the reduction gearing and the nut, also part of the lead screw and motorshaft; the casing providing a rigid support for the solenoid and the braking disk: the clutchk having the second magnetizable plate supported slidably by the lead screw; a portion of the reduction gearing being supported by the lead screw, and another portion of the reduction gearing being supported by the braking disk. A

4. A power driven jack construction comprising a reversible electric motor having a hollow armature shaft, a jack screw journalled in said hollow shaft and axially slidable therein, a hollow sleeve slidably and rotatably mounted on said jack screw, electromagnetic clutching and brake elements associated with said armature shaft and sleeve operable to connect said sleeve for rotation with said armature shaft when said motor is energized and to disconnect said sleeve and brake the same when the motor is deenergized. a nut mounted on said Jack screw, means for restraining said nut against axial movement with respect to said screw whereby rotation of said nut causes axial feeding movement of said screw, and constant mesh reduction gearing interconnecting said sleeve and nut whereby power is transmitted to said nut to rotate the same.

5. In combination, an electric motor having a hollow shaft and a motor circuit; a solenoid in the motor circuit which is energized when the motor is energized; a lead screw slidable but nonrotatable within the hollow shaft; a clutch including a driving plate fixed to the motorshaft and a driven plate slidable on the lead screw and magnetized by the energized solenoid to move into engagement with the driving plate; a fixed brake disk; a spring' urging the driven clutch plate into engagement with the brake disk whenever the magnetization of the driven clutch plate has less power than the spring: a sun gear secured to the driven clutch plate to be rotated thereby; a ring gear surrounding said sun gear: idler gears rotatably supported on the nxed brake disk and each meshing with both the ring gear and sun gear; a nut secured to the ring gear to rotate therewith and meshing with the lead screw to reciprocate the same when rotated; and power take-oi! means on one end of the lead screw.

HOWARD M. HOCOY. 

